Mendocino is one of the 58 counties in the state of California. It was created in 1850, making it one of the original counties in the state. As of the 2010 census, the population was 87,841, up from 86,265 in 2000. The county seat and largest city is Ukiah. The county encompasses 3,878.14 square miles (10,044.3 km2), of which 3,508.97 square miles (9,088.2 km2) is dry land.
Mendocino is bordered on the west by the Pacific Ocean, on the north by Humboldt and Trinity counties, on the northeast by Tehama County, the east by Glenn County, the southeast by Lake County, and on the south by Sonoma County. Mendocino happens to be the mainland county closest to the state of Hawai'i, a mere 2,265 miles to the southwest.